1. Technical Field of the Invention
The present invention relates to a mobile terminal device and a method for radiating heat therefrom, more particularly, to a structure of a circuit board in a mobile terminal device, on which heat-generating components are mounted, and to a method for radiating heat using the circuit board.
2. Description of the Related Art
Mobile terminal devices as typified by mobile phones are provided with various functions, such as a video phone function, a photographing function and a TV broadcast receiving function, in addition to a voice communications function and a mail sending/receiving function. For the purpose of realizing these functions, efforts have been made to improve the processing capacities of mobile terminal devices. As mobile terminal devices are made high in function and performance, the power consumed in the electronic components mounted inside the mobile terminal devices increases. As a result, the temperature rises in the mobile terminal devices have lead to problems.
For the purpose of preventing the temperature rises described above, countermeasures are taken in electronic apparatuses, such as personal computers. For example, heat-radiating heatsinks made of metal, fans, etc., are installed on the surfaces of electronic components that generate much heat so that heat can be radiated from the inside of the housing to the outside. In addition, Japanese Published Unexamined Patent Application No. Hei 11-95871 discloses a heat-radiating structure of an electronic apparatus, wherein heat conduction films are provided on ribs that are used to raise the rigidity of the housing of a mobile personal computer, and heat radiation plates bonded to heat generating components are made so as to contact with the heat conduction films of the ribs so that the heat generated from the heat generating components is dispersed efficiently.
However, since mobile terminal devices of recent years have been requested to be reduced farther in size and thickness, it is difficult to provide such heat-radiating structures as used in personal computers because of space limitations. Hence, in a mobile terminal device, it is necessary to transfer the heat generated in electronic components to the housing and to radiate the heat from the housing to the outside. However, the surface area of the housing of the mobile terminal device is small and does not have sufficient heat-radiating efficiency. Hence, if the amount of heat generated in the electronic components is large, the temperature of the housing eventually rises.
In addition, mobile terminal devices are also required to be reduced in thickness, the clearance between the electronic components and the housing cannot be increased, and the heat generated in the electronic components is transferred immediately to the surface of the housing. As a result, a problem of local temperature rising at the surface of the housing result.
In particular, if the temperature of the operation member, such as the keys that the user operates, and the temperature of the housing in the vicinity thereof are raised, discomfort is given to the user during operation. For this reason, it is desired to propose a mobile terminal device capable of effectively radiating the heat generated in electronic components.